A kinetic study of the lipase-catalyzed ethanolysis of two short-chain triradylglycerols: Alkylglycerols vs. triacylglycerols

This is the author’s version of a work that was accepted for publication in Journal of Molecular Catalysis B: Enzymatic. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Journal of Molecular Catalysis B: Enzymatic, 64, (2010) DOI 10.1016/j.molcatb.2010.02.010Lipase-catalyzed ethanolysis of two short-chain triradylglycerols, namely tributyrin and 2,3-dibutyroil- 1-O-alkylglycerols, have been studied. Much faster rate of reaction for the ethanolysis of tributyrin than that of 2,3-dibutyroil-1-O-alkylglycerols was attained. A kinetic model for the rate of release of ethyl butyrate and for the inactivation of the lipase has been also studied. The parameter corresponding to the release of ethyl butyrate was one order of magnitude higher for ethanolysis of tributyrin than the corresponding of 2,3-dibutyroil-1-O-alkylglycerols. On the contrary, the stability of Novozym 435 during ethanolysis of 2,3-dibutyroil-1-O-alkylglycerols was higher than the corresponding of tributyrin. At the reaction conditions under study, both ethanolysis reactions take place with high selectivity and yield monoesterified alkylglycerols and sn-2 monobutyrin as the main acylglycerols in the reaction mixtures.This work was supported by the projects AGL2006-02031/ALI and AGL2008-05655 by Ministerio de Ciencia (Spain) and also by Comunidad Autonoma de Madrid (ALIBIRD, project number S-505/AGR-0153) and Consolider-Ingenio FUN-C-FOOD (CSD2007- 00063)

An Update on the Therapeutic Role of Alkylglycerols

Scandinavian folk medicine used shark liver oil for the treatment of cancers and other ailments based on the rarity of tumors in sharks and their ability to resist infections. Shark liver oil is a source of alkylglycerols which have been studied as anti-cancer agents in several clinical trials. Moreover, alkylglycerols have been investigated for the treatment of radiation induced side effects and for their ability to boost the immune system. Several experimental studies have shown the ability of alkylglycerols to open the blood brain barrier to facilitate the access of therapeutic drugs to the central nervous system. This review covers the most important studies of alkylglycerols in both animals and humans

Multiple Beneficial Health Effects of Natural Alkylglycerols from Shark Liver Oil

Alkylglycerols (alkyl-Gro) are ether lipids abundant in the liver of some elasmobranch fish species such as ratfishes and some sharks. Shark liver oil from Centrophorus squamosus (SLO), or alkyl-Gro mix from this source, have several in vivo biological activities including stimulation of hematopoiesis and immunological defences, sperm quality improvement, or anti-tumor and anti-metastasis activities. Several mechanisms are suggested for these multiple activities, resulting from incorporation of alkyl-Gro into membrane phospholipids, and lipid signaling interactions. Natural alkyl-Gro mix from SLO contains several alkyl-Gro, varying by chain length and unsaturation. Six prominent constituents of natural alkyl-Gro mix, namely 12:0, 14:0, 16:0, 18:0, 16:1 n-7, and 18:1 n-9 alkyl-Gro, were synthesized and tested for anti-tumor and anti-metastatic activities on a model of grafted tumor in mice (3LL cells). 16:1 and 18:1 alkyl-Gro showed strong activity in reducing lung metastasis number, while saturated alkyl- Gro had weaker (16:0) or no (12:0, 14:0, 18:0) effect. Multiple compounds and mechanisms are probably involved in the multiple activities of natural alkyl-Gro

First insights into structure-function relationships of alkylglycerol monooxygenase

Alkylglycerol monooxygenase is a tetrahydrobiopterin-dependent enzyme that cleaves the O-alkyl-bond of alkylglycerols. It is an exceptionally unstable, hydrophobic membrane protein which has never been purified in active form. Recently, we were able to identify the sequence of alkylglycerol monooxygenase. TMEM195, the gene coding for alkylglycerol monooxygenase, belongs to the fatty acid hydroxylases, a family of integral membrane enzymes which have an 8-histidine motif crucial for catalysis. Mutation of each of these residues resulted in a complete loss of activity. We now extended the mutational analysis to another 25 residues and identified three further residues conserved throughout all members of the fatty acid hydroxylases which are essential for alkylglycerol monooxygenase activity. Furthermore, mutation of a specific glutamate resulted in an 18-fold decreased affinity of the protein to tetrahydrobiopterin, strongly indicating a potential important role in cofactor interaction. A glutamate residue in a comparable amino acid surrounding had already been shown to be responsible for tetrahydrobiopterin binding in the aromatic amino acid hydroxylases. Ab initio modelling of the enzyme yielded a structural model for the central part of alkylglycerol monooxygenase where all essential residues identified by mutational analysis are in close spatial vicinity, thereby defining the potential catalytic site of this enzym

Different behaviour of the N-terminal and C-terminal fragment of proatrial natriuretic factor in plasma of healthy subjects as well as of patients with cirrhosis

N-terminal (atrial natriuretic factor (ANF) 1-98) and C-terminal (ANF 99-126) fragments of proatrial natriuretic factor (NTA and CTA, respectively) were determined in plasma of healthy subjects adopting different postures and in patients with cirrhosis. Seven healthy subjects were investigated while seated and 30 min after assuming a horizontal position. NTA plasma concentrations increased in subjects in the horizontal position (from 734±250 (SE) fmol/ml to 9021227 fmol/ml; p<0.05). In contrast, CTA plasma concentrations remained unchanged (9.2+1.3 fmol/ml vs 8.9±1.6 fmol/ml). In 10 patients with cirrhosis of the liver, NTA concentrations were markedly (p<0.001) elevated compared to 11 healthy subjects (2334±291 fmol/ml vs 743±155 fmol/ml). However, there was no difference of CTA plasma levels between cirrhotic patients and healthy subjects (8.7±1.3 fmol/ml vs 8.2±0.9 fmol/ml). These data demonstrate changes of the plasma concentration of the N-terminal fragment of proatrial natriuretic factor by posture and in liver disease, in contrast to unchanged levels of the C-terminal fragment

Hexadecylphosphocholine, a new ether lipid analogue. Studies on the antineoplastic activity in vitro and in vivo.

Hexadecylphosphocholine (He-PC) is a new compound synthesized according to the minimal structural requirements deducted from studies with other ether lipids. In vitro studies on He-PC revealed remarkable antineoplastic activity on HL60, U937, Raji and K562 leukemia cell lines. In addition, He-PC, applied orally, showed a superior effect in the treatment of dimethylbenzanthracene-induced rat mammary carcinomas when compared to intravenously administered cyclophosphamide. After oral application He-PC was well absorbed from the intestine and metabolized in the liver by phospholipases C and D. During a 5-week treatment no hematotoxic effects were detected. In a clinical pilot study on breast cancer patients with widespread skin involvement, topically applied He-PC showed skin tumor regressions without local or systemic side effects